Worker bees reboot brain genes to suit the task

Worker honeybees shuttling between foraging and nursing tasks have been found to switch huge groups of genes on and off in their brains for each job.

This shows for the first time that different behaviours can have specific gene patterns.

The discovery could have implications for how our own behaviour influences which genes are switched on in our brains and bodies.

The changes were recorded for the first time when a group of worker honeybees (Apis mellifera), all starting life as "nurses", switched to being "foragers" but were then tricked by the researchers into becoming nurses again.

Most worker honeybees begin life as nurse bees, which feed the queen and her larvae. After 2 to 3 weeks, most nurses switch to being foragers. Andrew Feinberg of Johns Hopkins University School of Medicine in Baltimore, Maryland and his colleagues emptied a hive of all existing nurses. This tricked foragers into changing roles: as they returned from a bout of foraging, some reverted to being nurses to save the queen and the larvae.

To see what effect the role-play had on their brains, Feinberg and his colleagues scanned the insects' brain cell DNA for evidence of a process called epigenetic modification.

This is a way of switching on sets of genes that involves adding or removing chemical "methyl" tags to their DNA. Methylation enables large groups of genes to be simultaneously and reversibly switched on or off without altering the underlying genome sequence.

Feinberg and his colleagues noticed a specific pattern for each task – nursing or foraging. What's more, when foragers reverted to being nurses, they deactivated the "forager" gene pattern and rebooted the set needed for nursing.

The genetic changes were dramatic: as many as 150 genes were affected. Feinberg says it's difficult to say whether the change in behaviour caused the genetic switch or vice versa.

"It's the first evidence, to our knowledge, of an epigenetic change linked to reversible behaviour in any organism," says Feinberg. "It opens doors to new ways of thinking about human problems like addiction, and about learning and memory."

Psychiatric disorders like addiction, schizophrenia and bipolar disorder, as well as ageing and other chronic conditions like obesity are known to have an epigenetic component. So a better understanding of how epigenetics and behaviour interact could lead to new treatments.

"[Feinberg and colleagues] provide convincing evidence for a role of DNA methylation as a driver of complex behaviours," says David Sweatt of the University of Alabama at Birmingham, and a world authority on epigenetics.

Journal reference: Nature Neuroscience, DOI: 10.1038/nn.3218

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